The present invention relates to electronic circuit packages with dendrites connecting two conductive surfaces and method for producing same. The dendrites electrically connect the two conductive surfaces and provide coplanarity such that planarization process steps can be eliminated.
Electronic circuits contain many (sometimes millions) of components such as resistors, capacitors, inductors, diodes, electromechanical switches, and transistors. High density packaging of electronic components is particularly important to allow fast access to large amounts of data in computers. High density electronic circuit packages also are important in high frequency devices and communications devices. The components are connected to form circuits and circuits are connected to form functioning devices. The connections perform power and signal distribution. In a multi-layer electronic circuit package, some layers of the package serve as power planes and other layers serve as signal planes, depending on the operational requirements of the device. The devices require mechanical support and structural protection. The circuits themselves require electrical energy to function. The functioning devices, however, produce heat, or thermal energy which must be dissipated so that the devices do not stop functioning. Moreover, while high density packaging of a number of components can improve performance of the device, the heat produced by the power-consuming components can be such that performance and reliability of the devices is adversely impacted. The adverse impact arises from electrical problems such as increased resistivity and mechanical problems such as thermal stress caused by increased heat.
Electronic circuit packages, such as chips, modules, circuit cards, circuit boards, and combinations of these, thus must meet a number of requirements for optimum performance. The package must be structurally sturdy enough to support and protect the components and the wiring. In addition, the package must be capable of dissipating heat and must have a coefficient of thermal expansion that is compatible with that of the components. Finally, to be commercially useful, the package should be inexpensive to produce and easy to manufacture.
High density packages necessarily involve increased wiring density and thinner dielectric coatings between layers in a multi-layer electronic circuit package. The layers in a multi-layer package typically are electrically connected by vias and through-holes. The term xe2x80x9cviaxe2x80x9d is used for a conductive pathway between adjacent layers in a multi-layer electronic circuit package. The term xe2x80x9cthrough-holexe2x80x9d is used for a conductive pathway that extends to a non-adjacent layer. For high density packages the through-holes are increasingly narrow in diameter and the through-holes in each layer must be aligned precisely. This invention provides an alternative means of interconnectionxe2x80x94namely electrical interconnection using dendrites.
Furthermore, in creating a multi-layer electronic circuit package, particularly an organic package, metal circuits on the surface contribute to non-planar surfaces in the manufacturing process. To solve the problem of non-planar surfaces, many techniques of planarization are known in the art. However, these techniques require added processing steps. An object of this invention is to provide xe2x80x9cautomaticxe2x80x9d planarization by means of dendrites used for interconnection between conductive layers of the electronic circuit package such that the need for additional planarization steps in the manufacturing process is eliminated.
It is an object of this invention to provide an electronic circuit package with dendrites forming electrical connections between a first conductive layer and second conductive layer.
A further object of this invention is to provide an electronic circuit package that is inherently planarized using dendrites, thereby eliminating the need for planarization steps in the manufacturing process of the electronic circuit package.
A third object of this invention is to provide methods of fabrication of electronic circuit packages with dendrites forming electrical connections between a first conductive layer and a second conductive layer.
A fourth object of this invention is to provide an electronic circuit package and method for producing said package with dendrites forming electrical connections between a first conductive layer and a second conductive layer that is a ball grid array.
Accordingly, a method is provided for connecting two conductive layers in an electronic circuit package comprising the steps of forming dendrites on selected regions of a first conductive layer, applying an insulation material over the first conductive layer such that the dendrites are exposed through the insulation material to leave a substantially planar surface of exposed dendrites, and placing a second conductive layer on top of the exposed dendrites. Also claimed is an electronic circuit package incorporating the dendrites used for electrical interconnection and planarization manufactured in accordance with the present invention.
It is an advantage of the present invention that the dendrites provide electrical connection between two conductive layers of the electronic circuit package.
It is a further advantage that the dendrites provide a substantially planar surface for attachment of the second conductive layer without the need for additional planarization steps in the process of manufacturing the electronic circuit package.